Bidspirit auction | Worldwide Air Post Stamps and

Worldwide Air Post Stamps and Postal History - Russia and Soviet Union - 1931, Airship over the Arctic Region, 50k dark gray blue, error of color used in 1940 together with Stratostat ''C.C.C.P. 1'' 10k carmine and 20k violet on registered cover from Kiev to Riga, tied by ''9.11.40'' date stamps, boxed black postal handstamp ''Received in Kiev Train Station Post Office in damaged condition'' on reverse, violet ''Recommande'' marking and number ''5931'' placed upon arrival, no significant defects, F/VF and very rare usage of No. C23a, Est. $1,000-$1,200, Scott #C23a, C38-39